The insertion of pedicle screws into the spine for fixation has been commonly used for many years. In general, a set of implants is placed on both sides of the spinous process into the pedicles and the set on each side is connected by an individual rod. For example, in a single level fusion, whereby two vertebral bodies are intended to be fused together, four pedicle screws are used, two on each side of the spinous process. Each set of two is then connected by the rod. For multiple levels, more screws are used and connected by longer rods. The general technique is an open procedure, whereby the incision in the skin is long and spans the length of the affected area of the spine to be treated. To reach the spine, the incision is continued through the muscle. These long incisions are painful and require significant healing time. In some cases, where spinal pathology is complicated, this may be the only prudent approach. However, in many cases, a less traumatic procedure would be highly beneficial in reducing patient pain and speeding recovery time.
The current concepts for minimally invasive surgical approaches for placing pedicle screws generally fall into two basic forms. Sextant, which is an instrument covered under U.S. Pat. No. 6,530,929 to Justis et al. and U.S. Pat. No. 7,008,422 to Foley et al., uses an instrument that swings the connecting rod through an arc. This configuration requires that all the implants be on the arc. To accomplish this alignment, the implants are connected to towers that are subsequently connected together to create a single pivot point. The connecting rod must be swept around this pivot point to pass through all the implants connected to the towers. This procedure is very problematic. First, the spine is not a uniform curve. Disadvantageously, the instrument requires the spine to be forced into a uniform curve. Secondly, the pedicles are at angles that vary from level to level. This complicates placing of the instrument. To make such an instrument function, the number of implants that can be surgically connected is very limited. The second basic form for placing pedicle screws is that of attaching extensions, or towers, to the implants to lengthen the implant head. U.S. Pat. No. 7,955,355 to Chin describes extensions, although it does not teach the technique in which they are used to allow connecting rods to be placed. U.S. Pat. No. 7,918,858 to Stad et al. also describes extensions. The disclosure of U.S. Pat. No. 7,909,830 to Frigg et al. describes extensions and the surgical use of the extensions in conjunction with rod placement. These extended towers all have long slots in the sides. This is important to note, as rod placement by this approach is far too inaccurate to place directly within a spinal screw implant body. By extending the implant, it allows the surgeon to find the implant rod slot and introduce the rod higher and push it down until it seats in the implant body. There are self-evident issues with this approach. While less invasive than an open incision, there is muscle in the way, and the muscle must be split to allow the rod to slide downward into position within the spinal screw body. Secondly, the more screws the surgeon wishes to place, the more difficult the surgery becomes. Clearly such a procedure is limited in what it can do.
Therefore, while these prior minimally invasive spinal instruments and surgical procedures can be suitable for limited usage to which they somewhat address, they are not suitable to providing an instrument and surgical approach that can accurately and less traumatically place an implant connecting device over multiple levels.
Thus, a need exists to overcome the problems with the prior art systems, designs, and processes as discussed above.